The present invention is directed to an expansion anchor assembly for use in boreholes with an annular undercut formed in a receiving material. The assembly includes a threaded anchor bolt, a head part at the leading end of the anchor bolt first inserted into the borehole, and locking elements located around the anchor bolt and supported against the head part. A conical sleeve is arranged to contact the locking elements and displace them radially outwardly into the annular undercut. An abutment member is axially displaceable along the threaded anchor stud toward the leading end thereof for displacing the conical sleeve into expanding engagement with the locking elements.
In a known expansion anchor assembly, a conically shaped sleeve is displaced in the insertion direction of the expansion anchor into the borehole along a threaded anchor rod so that it displaces locking bodies radially outwardly into an undercut in the borehole. In the expanding operation, the conically shaped sleeve moves into a gap between the locking bodies and the anchor bolt.
The axial displacement of the conically shaped sleeve is effected by an abutment member in the form of a tensioning nut threaded onto the anchor bolt with a washer located between the nut and the conically shaped sleeve. Such an abutment also serves to secure a part onto the surface of the material into which the borehole is formed.
A considerable disadvantage of this known expansion anchor assembly is that the axial arrangement of the undercut determines the position of the abutment. Therefore, the correct axial arrangement of the undercut must be determined based on the thickness of the part to be secured by the expansion anchor assembly, that is, based on the different thicknesses of the parts,the undercut must be located in a different axial position.